Tsunami Source of the 2021 MW 8.1 Raoul Island Earthquake From DART and Tide-Gauge Data Inversion

The tsunami source of the 2021 MW 8.1 Raoul Island earthquake in the Kermadec subduction zone was estimated by inverting the tsunami signals recorded by Deep-ocean Assessment and Reporting of Tsunamis (DART) bottom pressure sensors and coastal tide-gauges. The main asperity of up to 5 m of slip is located northeastward from the hypocenter, with features compatible with the aftershock distribution and rapid back-projection analysis. Three earthquakes of MW ∼8 or larger which also produced moderate tsunamis happened in the 20th century in the same portion of the subduction zone. This is the first great tsunamigenic event captured by the new New Zealand DART network in the South West Pacific, which proved valuable to estimate a robust image of the tsunami source. We also show a first proof of concept of the capability of this network to reduce the uncertainty associated with tsunami forecasting and to increase the lead time available for evacuation for future alerts.